Lemma 5 ([1]})
Given \(x, y \in \mathbb {R}^{n}\)  in vector sample model, and query access to \(x\)  and \(y\) , the ability to sample from \(\mathcal {D}_x\) , one can approximate \(\langle x, y \rangle \)  to additive error \(\xi \Vert x\Vert \Vert y\Vert \)  with at least \(1 - \eta \)  probability using \(O(\frac{1}{\xi ^2}\, {\rm log}\frac{1}{\eta })\)  queries and samples.

